1. Field of the Invention
The invention relates to implantable medical stimulators, and more particularly to stimulators which produce an electrical stimulation signal.
2. Description of the Related Art
Epilepsy and other similar motor disorders are associated with abnormal neural discharge patterns. Several different treatment techniques and methods involving applying an electrical signal to stop or reduce seizures were described in U.S. Pat. No. 4,702,254 to Dr. Jacob Zabara, which patent is hereby incorporated by reference in this specification. One technique involved determining when an epileptic seizure was about to occur, and applying an electrical signal to the vagus nerve. The other technique suggested periodically applying a signal to the vagus nerve even if an aura or other condition was not sensed. Possible treatment periods were suggested. The patent further disclosed a high level block diagram of a circuit for applying electrical signals to the vagus nerve. The signals could be varied between stated limits. The limits were stated as being programmable by use of a reed switch whose openings and closings are controlled by an external programmer and electromagnet.
Conventional implantable medical stimulators such as pacemakers and drug infusion pumps are ordinarily based on custom integrated circuits which are quite complex, and therefore expensive, and use complicated pulse position communications techniques to transfer information between the implant and an external programmer. The custom circuitry is developed because of the need to keep power consumption at a minimum, the allowable size for implantable devices and the complexity of the communications techniques. The expense of the implanted unit and the programmer thus limits both the number of persons who can obtain the units and the number of hospitals, clinics and doctors which can program the units. Therefore it is undesirable to simply port over pacemaker technology for use in epileptic and other nervous system disorder patients.